Optical Draft Force Sensing for Tractor Reliability
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Solution Overview
Problem
Current draft force sensing systems for agricultural tractors are prone to environmental contamination, require frequent maintenance, and have reliability issues due to moving parts and exposure to mud and debris, leading to inaccurate readings and increased costs.
Innovation Solution
A draft force sensing system with sealed L-shaped draft bars and a sensing unit that includes pivotally mounted sensing arms, a resilient member, and a stop member, which generates a draft force signal based on the distance between the arms, reducing the need for maintenance and improving protection from environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current production draft force sensing systems are used with moving parts, then the system can measure draft force, but the system requires frequent maintenance and is prone to environmental contamination
Solution Approach 1:
The patent replaces the mechanical draft force sensing system with an optical system. A laser beam serves as the draft force indicator, eliminating physical moving parts that are susceptible to mud, dirt, and debris contamination. The system uses optical reflection and detection to measure draft force, substituting mechanical components with optical fields that are immune to environmental contamination.
Solution Approach 2:
The patent extracts the draft force measurement function from the mechanical domain and transfers it to the optical domain. By taking out the physical sensing elements (plungers, pins, bending bars) and replacing them with an optical indicator (laser beam), the system removes the components that are vulnerable to environmental harm while retaining the measurement capability.
2Measurement precision
If draft sensing pins with two instrument pins are used, then the draft force can be measured, but the cost increases and reliability decreases
Solution Approach 1:
The patent merges the functions of two separate instrument pins into a single optical indicator (laser beam). Instead of requiring two physical pins to measure draft force, the system uses one laser source that projects a beam whose position or characteristics indicate the draft force magnitude. This consolidation reduces the number of components from two to one, improving reliability while maintaining measurement precision.
3Measurement precision
If bending bar and draft sensing shaft systems with moving parts are used, then draft force can be sensed, but the system requires sealed compartments and occupies significant space
Solution Approach 1:
The patent replaces the mechanical bending bar and draft sensing shaft system with an optical laser beam indicator. This substitution eliminates the need for sealed compartments to protect moving parts and dramatically reduces the space required for the sensing system. The optical field occupies minimal space compared to the physical mechanical components it replaces.
4Measurement precision
If spring steel strap and sensor plunger system is used, then draft force can be measured, but the zero load voltage adjustment is inconsistent and requires frequent calibration
Solution Approach 1:
The patent replaces the spring steel strap and sensor plunger mechanical system with an optical laser-based system. This eliminates the need for manual zero load voltage adjustment and calibration procedures. The optical system inherently provides consistent reference points through the laser beam geometry, removing the calibration complexity associated with mechanical adjustment of spring straps and plunger positions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides accurate draft force measurements with reduced maintenance requirements, increased reliability, and cost-effectiveness by minimizing exposure to debris and eliminating the need for periodic lubrication, while requiring minimal space and using a single transducer for both draft links.
Implementation Method 1
A resilient member is coupled to the left and right sensing arms and biased to urge the left and right sensing arms towards each other
Implementation Method 2
A draft force transducer engages the longer arm portions of the left and right sensing arms, the draft force transducer generating a draft force signal representing a distance between the longer arm portions
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A draft force sensing system (30) for an agricultural tractor has left and right draft bars (32, 34) and a sensing unit (52). The sensing unit (52) comprises a housing (56). Laterally spaced apart left and right pivot pins (90, 92) are mounted in the housing (56). A left sensing arm (94) is pivotally mounted on the left pivot pin (90), the left sensing arm (94) having a shorter arm portion (104) movable in response to draft force applied to the left draft bar (32) and having a longer arm portion (102). A right sensing arm (96) is pivotally mounted on the right pivot pin (92), the right sensing arm (96) having an shorter arm portion (108) movable in response to draft force applied to the right draft bar (34) and having a longer arm portion (106). A resilient member (121) is coupled to the left and right sensing arms (94, 96) and biased to urge the left and right sensing arms (94, 96) towards each other. A stop member (123) is positioned between the left and right sensing arms (94, 96) and engagable with the left and right sensing arms (94, 96) to limit movement of the left and right sensing arms (94, 96) towards each other. A draft force transducer (119) engages the longer arm portions (102, 106) of the left and right sensing arms (94, 96), the draft force transducer (119) generating a draft force signal representing a distance between the longer arm portions (102, 106).